Buggy code:
public class StatementAdapter implements Statement { @ Override public < T > T unwrap ( Class < T > iface ) throws SQLException { } @ Override public boolean isWrapperFor ( Class < ? > iface ) throws SQLException { } @ Override public int executeUpdate ( String sql ) throws SQLException { } @ Override public void close ( ) throws SQLException { } @ Override public int getMaxFieldSize ( ) throws SQLException { } @ Override public void setMaxFieldSize ( int max ) throws SQLException { } @ Override public int getMaxRows ( ) throws SQLException { } @ Override public void setMaxRows ( int max ) throws SQLException { } @ Override public void setEscapeProcessing ( boolean enable ) throws SQLException { } @ Override public int getQueryTimeout ( ) throws SQLException { } @ Override public void setQueryTimeout ( int seconds ) throws SQLException { } @ Override public void cancel ( ) throws SQLException { } @ Override public SQLWarning getWarnings ( ) throws SQLException { } @ Override public void clearWarnings ( ) throws SQLException { } @ Override public void setCursorName ( String name ) throws SQLException { } @ Override public boolean execute ( String sql ) throws SQLException { <START_BUG> return false ; <END_BUG> } @ Override public ResultSet getResultSet ( ) throws SQLException { } @ Override public int getUpdateCount ( ) throws SQLException { } @ Override public boolean getMoreResults ( ) throws SQLException { } @ Override public void setFetchDirection ( int direction ) throws SQLException { } @ Override public int getFetchDirection ( ) throws SQLException { } @ Override public void setFetchSize ( int rows ) throws SQLException { } @ Override public int getFetchSize ( ) throws SQLException { } @ Override public int getResultSetConcurrency ( ) throws SQLException { } @ Override public int getResultSetType ( ) throws SQLException { } @ Override public void addBatch ( String sql ) throws SQLException { } @ Override public void clearBatch ( ) throws SQLException { } @ Override public int [ ] executeBatch ( ) throws SQLException { } @ Override public Connection getConnection ( ) throws SQLException { } @ Override public boolean getMoreResults ( int current ) throws SQLException { } @ Override public ResultSet getGeneratedKeys ( ) throws SQLException { } @ Override public int executeUpdate ( String sql , int autoGeneratedKeys ) throws SQLException { } @ Override public int executeUpdate ( String sql , int [ ] columnIndexes ) throws SQLException { } @ Override public int executeUpdate ( String sql , String [ ] columnNames ) throws SQLException { } @ Override public boolean execute ( String sql , int autoGeneratedKeys ) throws SQLException { } @ Override public boolean execute ( String sql , int [ ] columnIndexes ) throws SQLException { } @ Override public boolean execute ( String sql , String [ ] columnNames ) throws SQLException { } @ Override public int getResultSetHoldability ( ) throws SQLException { } @ Override public boolean isClosed ( ) throws SQLException { } @ Override public void setPoolable ( boolean poolable ) throws SQLException { } @ Override public boolean isPoolable ( ) throws SQLException { } @ Override public ResultSet executeQuery ( String sql ) throws SQLException { } @ Override public void closeOnCompletion ( ) throws SQLException { } @ Override public boolean isCloseOnCompletion ( ) throws SQLException { } }

Fix:
return ( executeQuery ( sql ) ) != null ;